It has become increasingly important to transport thin workpieces, such as semiconductor wafers and substrates for magnetic disks, from a cassette into, through and out of a vacuum processing system, and back into a cassette. One such system is described in U.S. Pat. No. 4,500,407 which is assigned to the assignee of the present invention and which is incorporated herein by reference.
The above-referenced system has performed extremely well in important semiconductor wafer coating applications and in coating magnetic disk substrates for use in computer memory applications. However, the above system has throughput limitations since each processing station in the referenced system is designed to accommodate a single workpiece and the transport system described in this prior art system is designed to transfer a single workpiece from an entrance load lock sequentially through a plurality of processing stations to an exit load lock.